This application relates to removing matter on a fluid surface of a tank.
It is known to use coating fluid reservoirs or xe2x80x9cdip tanksxe2x80x9d to apply photoreceptor coating solution to coat photoreceptor devices such as photoreceptor flexible belts and cylindrical-shaped drums. For example, in the commonly-assigned U.S. Pat. No. 5,681,392 by Eugene A. Swain, entitled xe2x80x9cFluid reservoir containing panels for reducing rate of fluid flow,xe2x80x9d issued Oct. 28, 1997, the fluid reservoir (equivalent to a dip tank) 10 is used to supply organic photoreceptor coating fluid 80 to coat a flexible belt-type photoreceptor substrate 60.
In this coating process, a photoreceptor substrate (belt or drum) is immersed or xe2x80x9cdippedxe2x80x9d into the orifice of a tank containing the solution to be coated and then withdrawn at a rate that controls the coating thickness. The usual mechanism to coat the substrate is to pump a coating solution containing the active materials, either dissolved or in suspension (such as pigments), into the tank from an inlet located in the bottom of the dip tank and continuously overflow the tank at the orifice located at the top of the tank. In this way the substrate is subjected to a uniform flow of solution relative to the coating speed.
There are several problems in the dip coating process which can result in defects on the coated substrate surface.
In one such problem, for example, sometimes foreign matter such as bubbles or particles are introduced into the coating solution due to various causes. These foreign materials remain on the surface of the coating solution even when there is overflow from the dip tank, thereby causing problems in quality and yield, such as streaks and resist spots.
Moreover, current dip tanks provide coating solution flow that is symmetric for flow and thickness uniformity. However, such symmetry is undesired in order to remove entrained foreign matter that may be trapped in the center of the coating solution by vortices. Also, bubbles caused by dipping photoreceptor drums also tend to adhere to the surface of the drum.
As a result, there is a need for a method and an apparatus for removing matter on a fluid surface of a tank.
In one aspect of the invention, there is described a method for removing matter on a fluid surface of a tank, the tank defining a tank orifice comprising a tank orifice rim, the tank orifice rim containing a fluid surface of a fluid, the fluid overflowing the tank orifice rim to form a fluid overflow, the fluid surface defining a fluid surface center, the method comprising discharging a plurality (n) of jets of the fluid towards the fluid surface center.
In another aspect of the invention, there is described an apparatus for removing matter on a fluid surface of a tank, the tank defining a tank orifice comprising a tank orifice rim, the tank orifice rim containing a fluid surface of a fluid, the fluid overflowing the tank orifice rim to form a fluid overflow, the fluid surface defining a fluid surface center, the apparatus comprising means for discharging a plurality (n) of jets of the fluid towards the fluid surface center.